Shielded electrical cables, including twisted shielded pairs (TSPs) of wires, are a common feature of many electrical designs, due to their inexpensive construction and good resistance to electromagnetic interference. But it has been a challenge to make twisted shielded pairs with the small diameters that are preferable in the construction of biomedical devices, as well as other applications.
It is typical to form a TSP creating a twisted pair of insulated wires, serving bare conductive wires about this twisted pair and then running the resultant work piece through a bath of melted polymer, thereby placing a protective coating of polymeric insulation about the shield. Using this technique it has been difficult to form a twisted shielded pair having a uniform diameter over its length, and having a diameter of less than 0.2 mm. For those using twisted shielded pairs for biomedical applications, it is desirable to be able to produce this product with diameters smaller than 0.2 mm. Having a uniform diameter over the length of the TSP is also desirable.